Just got the encoder so far (without major type 6, i.e. tagging) and the code is pretty messy and possibly not 100% correct, but it's true that the amount of code required is pretty minimal.
Update: Fixed a bunch of bugs in the encoder and have a working decoder as well. Still no tagging, but you can encode/decode pretty much anything you could with a naive JSON implementation.
Just got the encoder so far (without major type 6, i.e. tagging) and the code is pretty messy and possibly not 100% correct, but it's true that the amount of code required is pretty minimal.